The present invention relates to multiple base compositions, for example for use as solid fuel rocket propellants. The compositions are particularly suitable for case-bonded rocket motors.
The term "multiple base composition" used herein refers to compositions employing plasticised nitrocellulose as a matrix. The matrix may carry additional ingredients such as fuels (eg metal particles), oxidisers (eg perchlorates, or nitramine), ballistic modifiers and burning rate stabilisers; this list is not exclusive, since other special additives are also known in the propellant art. The most common form of multiple base composition is the double base type, but triple base compositions are also found.
Double base compositions for use as propellants comprise nitrocellulose and an energetic plasticiser. The latter is usually a nitric ester, and nitroglycerine is most commonly used. Such compositions can be made "smokeless" more easily than "composite propellants" in which oxidisers are incorporated in an elastomeric binder.
In a case-bonded rocket motor, the propellant is bonded to the wall of the motor. This arrangement can provide optimum use of the space within the motor. Similar arrangements may be used in other gas generators using propellant compositions, eg engine starter power cylinders.
Problems are sometimes encountered when case-bonded, double base compositions are exposed to very low storage temperatures. Such compositions commonly have low strain capability at such temperatures, and they may be subjected to stress because of differential expansion and contraction of the casings and propellant composition.